EP 1 561 542 A1 has disclosed a method for removing a layer of a component. It involves a layer composed of an organic binding agent, which is to be removed from a substrate without damaging the substrate. To this end, a blasting jet of dry ice particles is guided over the surface so that the action of the dry ice particles removes material from the layer containing an organic binding agent. The dry ice removal is intended to avoid a contamination with foreign substances and to not harm the metallic base body of the component.
EP 1 321 625 B1 has disclosed a method for removing a metal layer in which a layer system includes the metal layer and a substrate coated by the metal layer and in which the removal process is a blasting process. The blasting process here can be a sand blasting process in which the metal layer is powerfully cooled in order to achieve a low-temperature embrittlement of the coating in relation to the substrate.
EP 1 034 890 A2 has disclosed a method and device for blasting with different blasting media. Its intent is to achieve an abrasive blast treatment with blasting media in which the abrasive action of the blasting media lies between that of blasting media that are in fluid form under normal conditions and that of blasting media that are in a solid aggregate state under normal conditions. In this case, a mixture of a first blasting medium such as dry ice and a second abrasive blasting medium such as sand is used.
DE 199 46 975 C1 has disclosed a device and method for removing a coating from a substrate, which is intended to be gentle to the material and suitable for removing both soft and hard coatings. According to this method, a cold treatment is carried out by blasting with a coolant, which results in an embrittlement of the coating, and then an abrasive cleaning action is carried out with a machining tool; because of the cold treatment, the mechanically abrasive machining can be carried out with tool parts that are not as hard as machining tools according to the prior art.
DE 199 42 785 A1 has disclosed a method for removing solid machining residues, surface coatings, or oxide layers; the intent is for a cleaning to take place only in locations where solid machining residues are present. The cleaning in this case can be carried out with steam jets, dry ice jets, or by cleaning with technically induced shock waves, so-called laser cleaners. The CO2 cleaning can be carried out using intrinsically known dry ice pellets.
DE 102 43 035 B4 has disclosed a method and device for removing layers that form on metal components due to heating and cooling. When removing for example cinders, oxide silicate, and slag coatings on metal work pieces and in particular, metal work pieces with uneven surfaces such as axle components and autobody components for motor vehicles, since the solid particles in abrasive compressed gas jets do not completely remove the layers from metal work pieces in all cases, the flow of compressed gas used to project e.g. dry ice particles at the metal work piece to be cleaned should be preheated and should have a temperature that is greater than the temperature of the air surrounding the metal work piece and/or the surface temperature of the metal work piece. This should assure on the one hand, that the metal work piece is not cooled too intensely and on the other hand, that the compressed gas is at least essentially free of moisture so as to avoid an undesirable formation of condensation. The layers to be removed from the surface of the metal piece are removed by means of the mechanical action of the dry ice particles, which strike it at a high velocity and therefore have an abrasive action, and by means of the dry ice particle-induced, localized cooling of the surface and coating.
WO 2005/021822 of the applicant has disclosed a method for protecting a cathodic anticorrosion layer by adding—within certain limits—oxygen-affinity elements to the metal composing the cathodic protective layer in order to protect the cathodic protective layer during the hardening of a component manufactured from the cathodically protected metal. To harden components of this kind, they must be heated to a temperature above the austenitizing temperature of the base metal, in this case steel. Particularly with high-hardening steels, this temperature is above 800° C. At such temperatures, most cathodic protective layers are destroyed by evaporation or oxidation so that a component treated in this way would not have any cathodic protection after hardening. Because oxygen-affinity elements have been added, the oxygen-affinity elements diffuse out of the compound composing the cathodic protective layer and migrate to the surface, forming a very fine protective layer there. This very fine protective layer can, for example, be composed of magnesium oxide, aluminum oxide, or mixtures thereof. WO 2005/021820 has also disclosed using a method of this kind in roll profiling.
The object of the present invention is to create a method with which it is possible to improve paint adhesion to hardened steel components provided with a cathodic protective layer.